Stab-type coupling with collet having locking ribs and rotation prevention member

ABSTRACT

A coupling receives a non-metallic tube ( 12 ) in an opening of a coupling body ( 10 ). A seal assembly ( 22, 24 ) disposed inside the coupling body ( 10 ) seals between the body ( 10 ) and the tube ( 12 ). A collet ( 16 ) disposed in the coupling body ( 10 ) includes a tapered external surface ( 50 ) that engages a tapered wall in the coupling body ( 10 ) to resist pull-out of the tube ( 12 ). The collet ( 16 ) includes an inner toothed ( 52 ) surface for gripping the tube ( 12 ) and has a split ( 70 ) or slots ( 54 ) that allow the collet ( 16 ) to radially expand and contract. A rotation prevention member, which in a preferred embodiment is a longitudinal rib ( 56 ) extending inwardly from the collet ( 16 ), limits relative rotation between the collet ( 16 ) and the tube ( 12 ). Moreover, edges ( 74 ) of the split ( 70 ) are rounded so that the collet can rotate relative to the coupling body ( 10 ).

This application claims priority from provisional patent applicationSerial No. 60/035,480, filed Jan. 13, 1997.

BACKGROUND OF THE INVENTION

Stab-type couplings for connecting smooth walled non-metallic pipes areknown, for example, in U.S. Pat. No. 4,229,025 which is incorporatedherein by reference.

These couplings are particularly useful for connecting lengths ofplastic pipe, such as plastic pipe used in transmission of natural gas.These stab-type couplings include a tapered, non-metallic coupling bodysurrounding a coupler assemble which receives the end of a plastic pipe.The coupler assembly inside the coupling body includes a hollow inserttube which fits inside the end of the pipe and a retaining collet whichgrips an exterior surface of the pipe. The collet is a generally taperedmember having a series of circumferential interior teeth for grippingthe pipe. The collet also includes a plurality of longitudinallyextending recesses which allow the collet to expand and contract asnecessary to receive and hold the pipe. The coupler assembly alsoincludes various spacing and sealing members within the coupler body.

The coupler body of the known stab-type coupling is generally attachedat one end to another member such as a male or female threaded member, aT-shaped or L-shaped member, or a second coupler body so that a pipe canbe coupled to one or more other pipes or other members. A single couplerbody of the type disclosed in the '025 patent is shown in FIG. 1. Inoperation, a free end of a plastic pipe is pushed into the stab-typecoupling from the right side of the coupling as shown in the FIGURE.Once the pipe is inserted, the collet prevents the pipe from beingremoved because attempted pull-out of the pipe will cause the collet tomove to the right in the Figure engaging a tapered stainless steelback-up ring which is molded into the interior of the coupling body andcausing the sharp interior teeth of the collet to grip the exterior ofthe pipe. Sealing of the pipe is actually performed by the sealingO-rings provided within the coupling.

The interior teeth of the collet have relatively sharp edges which biteinto the pipe and do not allow it to be removed by pulling axially onthe pipe. However, the collet having interior circumferential teeth willallow the pipe to be removed or loosened when the pipe is rotated withinthe collet achieving an unscrewing action.

For example, it has been found that the coupling described in the '025patent can become unscrewed from the coupling either intentionally orunintentionally by rotating the plastic pipe with respect to the colletand coupling body.

In order to prevent the possibility of unscrewing a plastic pipe from astab-type coupling, a collet has been designed as shown in the drawings.

SUMMARY OF THE INVENTION

The present invention contemplates a new and improved stab-type couplingthat overcomes the above-referenced problems and others and provides asimple, economical solution to these problems.

According to the present invention, there is provided a coupling thatreceives a non-metallic tube end. The coupling includes a body having anopening at one end that receives the tube end and a seal assemblyreceived in the body that seals between the body and tube end. A colletdisposed in the coupling body has an external tapered surface thatengages a tapered wall of the coupling body cavity to resist pull-outforces. The collet further includes an inner toothed surface that gripsthe non-metallic tube end. A rotation prevention member, such as alongitudinal rib, extends inwardly from the collet and prevents relativerotation between the collet and tube.

According to another aspect of the invention, the collet is split by oneor more slots that allow the collet to radially expand and contract.Edges of the split may be rounded to allow the collet to rotate relativeto the coupling body.

A principal advantage of the invention is the ability to provide astab-type coupling in which the tube end cannot be rotatably withdrawn.

Still another advantage of the invention resides in the ease with whichthe solution is accomplished.

Yet another advantage of the invention is associated with the smoothedges that allow the collet to rotate relative to the body.

Still other advantages and benefits of the invention will becomeapparent to others upon reading and understanding the following detaileddescription.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The invention may take physical form in certain parts and arrangementsof parts, preferred embodiments of which will be described in detail inthis specification and illustrated in the accompanying drawings,wherein:

FIG. 1 is a cross sectional side view of a stab type coupling;

FIG. 2 is an end view of a first embodiment of a retaining collet;

FIG. 3 is a partial cross sectional side view of the retaining collet ofFIG. 2, taken along line 3—3;

FIG. 3A is an enlargement of a portion of FIG. 3;

FIG. 4 is an end view of a second embodiment of a retaining collet;

FIG. 4A is an enlargement of a portion of FIG. 4;

FIG. 5 is a partial cross sectional side view of the retaining collet ofFIG. 4, taken along line 5—5;

FIG. 5A is an enlargement of a portion of FIG. 5; and

FIG. 6 is an opposite end view of the collet of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to the drawings, which illustrate preferred embodiments ofthe invention only and are not intended to limit the invention, thestab-type coupling includes a non-metallic coupling body 10 whichreceives the end of a non-metallic tube or pipe 12. The interior surfaceof the coupling body 10 includes a metallic back up ring 14 molded intothe coupling body and defining a generally frusto-conical surface whichcooperates with a retaining collet 16. A reinforcing stiffener or hollowinsert 18 defines an internal passage of the coupling for allowing fluidto pass through the coupling. The hollow insert 18 is preferablychamfered at a first end 20 to assist in inserting the insert into thepipe 12.

Two O-ring seals 22, 24 are provided for sealing between the couplingbody 10 and the pipe 12. The O-ring seals 22, 24 are compressed when thepipe 12 is inserted into the coupling body. An annular retainer/spacerring 26 is positioned adjacent a flange or radial shoulder 28 of thehollow insert 18 to position the O-ring seals 22, 24 and provide supportfor the flange. In addition, a thrust washer 32 functions to positionthe O-ring seals 22, 24. The retainer/spacer ring 26 preferably includesinterior teeth 30 which grip the exterior of the pipe 12 and cause theO-ring seals 22, 24 and washer 32 to move along with the pipe if thepipe is moved to the right in FIG. 1.

A first embodiment of a tubular retaining collet 16 which preventswithdrawal of the pipe 12 from the coupling body 10 is shown in FIGS. 2and 3. As best seen in FIG. 3, the collet 16 is tapered in shape and hasa smooth exterior surface 50 and an interior surface having a pluralityof circumferential teeth 52. The tapered exterior surface 50 is at anangle α with respect to an axis of the collet. The angle α is generallycomplementary to the angle of the interior surface of the back-up ring14 which is molded into the interior surface of the coupling body 10.

The tubular collet 16 is provided with generally longitudinallyextending splits defined by recesses or slots 54 located at an angle θ,approximately every 45 degrees, around the collet. The slots 54 permitcontraction of the collet about the pipe 12 when an attempt is made topull the pipe from the coupling. The slots 54 also allow the collet toexpand when the pipe 12 is inserted. As shown in FIGS. 1-3, the slots 54do not extend through the entire length of the collet but open on eitherthe first or the second end of the collet preferably in an alternatingmanner. Uninterrupted areas 58 are provided on alternating ends of thecollet. Different numbers and arrangements of slots 54 may be usedwithout departing from the invention.

In order to prevent the possibility of the plastic pipe 12 beingunscrewed from the coupling, the interior surface of the collet 16 hasbeen provided with one or more longitudinal raised ribs 56 extendingalong one or more edges of the slots 54. As shown in the detail of FIG.3A the raised rib 56 interrupts the teeth 52. The rib 56 preferably hasa height which is substantially equal to the height of the pointed teeth52. This interruption of the teeth 52 by the ribs 56 will prevent thepipe 12 from rotating with respect to the collet 16 and thus, preventsunscrewing of the pipe from the coupling.

Another embodiment of a collet 60 for use in the stab-type coupling ofFIG. 1 for preventing withdrawal of a pipe from the coupling is shown inFIGS. 4-6. The collet 60 is a single split design (i.e., the splitextends over the entire longitudinal having an exterior smooth surface62 and an interior surface having teeth 64. The collet has two edgesurfaces 66, 68 formed by the single split 70 which is provided to allowthe collet to expand and contract around the pipe. The edge surfaces 66,68 include a longitudinal rib 72 at the inside diameter of the colletand a longitudinal rounded or chamfered protrusion 74 at the outsidediameter of the collet. The ribs 72 interrupt the teeth 64 and preventthe collet 60 from rotating on a pipe. The collet 60 also includes alongitudinal smoothed surface 76 which has no teeth and extends from oneend of the collet to an opposite end.

It is desirable that while the collet does not rotate on the pipe, thecollet does freely rotate inside the tapered portion of the couplingbody 10. Therefore, the longitudinal protrusions 74 formed at each edgeof the split 70 have a rounded or chamfered corner 78 shown in FIG. 4A.The purpose and function of this chamfer 78 is to minimize thepossibility that the outer corner of the edges 66, 68 of the collet 60may bite into the internal diameter of the coupling body in a mannerwhich impedes the ability of the collet to rotate along with the pipe.Thus, the chamfered corner 78 prevents the corner from catching on theinterior surface of the coupling body.

The invention has been described with reference to the preferredembodiments. Obviously modifications and alterations will occur toothers upon reading and understanding this specification. It is intendedto include such modifications and alterations insofar as they comewithin the scope of the appended claims or equivalents thereof. Forexample, while the embodiments which have been illustrated in thedrawings include axial ribs to prevent rotation of the pipe inside thecollet, other structures may also be used to perform this function. Thecollet interior surface may include serrated teeth, nubs on the teeth,randomly tilted teeth, etc. In addition, the locations, number, andshape of the ribs may be varied without departing from the invention.

The coupling including a collet according to the present inventionallows reliable, quick, and secure connection of pipes.

The coupling provides a connection which cannot be unscrewed in themanner in which known stab-type couplings can be unscrewed.

Having thus described the invention, it is claimed:
 1. A coupling forreceiving an end of an associated non-metallic tube, the couplingcomprising: a coupling body having an opening dimensioned to receive anassociated non-metallic tube end and at one end communicating with aninternal cavity, the cavity including a tapered wall that convergestoward the opening; a seal assembly received in the coupling body cavityfor sealing between the coupling body and an associated non-metallictube end; a collet received in the coupling body cavity and having atapered external surface that engages the tapered wall of the cavity toresist pull-out of an associated non-metallic tube end, the colletfurther including an inner toothed surface for gripping an externalsurface of an associated non-metallic tube end and a split that allowsthe collet to radially expand and contract; and a circumferentiallydiscontinuous rotation prevention member extending from the collet alonga substantial portion of an axial length thereof to limit relativerotation between the collet and an associated non-metallic tube end. 2.The coupling of claim 1 wherein the split extends in a generallylongitudinal direction from a first end of the collet and terminatesbefore reaching a second end of the collet.
 3. The coupling of claim 2wherein the split is defined by multiple slots circumferentially spacedabout the collet.
 4. The coupling of claim 1 wherein the split isdefined by multiple slots circumferentially spaced about the collet. 5.The coupling of claim 1 wherein the split extends inwardly from ends ofthe collet and terminate before reaching an opposite end.
 6. Thecoupling of claim 5 wherein the split is defined by multiple slots thatextend generally longitudinally from opposite ends of the collet in analternating manner.
 7. The coupling of claim 1 wherein the rotationprevention member includes a rib extending radially inward from thecollet.
 8. The coupling of claim 1 wherein the rotation preventionmember includes first and second ribs disposed on opposite sides of thesplit.
 9. The coupling of claim 1 wherein the tapered wall of thecoupling body includes a metallic back-up ring.
 10. The coupling body ofclaim 1 further comprising a metallic insert sized for receipt in anassociated non-metallic tube and including a shoulder that is adapted toabut against an end of an associated non-metallic tube.
 11. A stab-typecoupling for connecting to an end of a smooth wall non-metallic tube,the coupling comprising: a coupling body having an opening at a firstend adapted to receive an associated non-metallic tube at least one sealmember received in the coupling body and dimensioned for sealing betweenan associated non-metallic tube end and the coupling body; a retainingcollet disposed in the coupling body having a tapered external surfacethat converges toward the first end and an internal toothed surfaceadapted to grip an associated non-metallic tube end, the colletincluding at least one slot allowing the collet to radially expand andcontract about an associated non-metallic tube end; and a rotationpreventing member between the collet and an associated non-metallic tubeend extending only linearly.
 12. The coupling of claim 11 wherein therotation preventing member includes a rib extending radially inward froman edge of the collet adjacent the slot.
 13. The coupling of claim 11wherein the rotation preventing member includes a pair of ribs extendingradially inward from either side of the slot.
 14. The coupling of claim11 further comprising smooth edges along the slot that allow freerotation between the collet and the coupling body.
 15. The coupling ofclaim 11 wherein the internal toothed surface includes circumferentiallyextending teeth and the rotation preventing means includes at least onegenerally longitudinally extending rib.
 16. The coupling of claim 11further comprising a tapered metallic back-up ring received in thecoupling body for operative engagement with the collet.
 17. The couplingof claim 11 further comprising a metallic insert dimensioned for receiptin a terminal end of an associated non-metallic tube.
 18. The couplingof claim 11 wherein the seal member is axially interposed between aback-up ring and a thrust ring.
 19. The coupling of claim 1 furthercomprising smooth edges along the split that allow free rotation betweenthe collet and the coupling body.
 20. A coupling for receiving an end ofan associated non-metallic tube, the coupling comprising: a couplingbody having an opening dimensioned to receive an associated non-metallictube end and at one end communicating with an internal cavity, thecavity including a tapered wall that converges toward the opening; aseal assembly received in the coupling body cavity for sealing betweenthe coupling body and an associated non-metallic tube end; a colletreceived in the coupling body cavity and having a tapered externalsurface that engages the tapered wall of the cavity to resist pull-outof an associated non-metallic tube end, the collet further including aninner toothed surface for gripping an external surface of an associatednon-metallic tube end and a split that allows the collet to radiallyexpand and contract; and a circumferentially discontinuous rotationprevention member extending from the collet to limit relative rotation